Japan’s Mitsubishi Aircraft expects to see flight testing of its delayed MRJ90 regional jet accelerate this summer, as engineers work to complete the design changes that led to the most recent schedule deferral by early autumn.

Speaking with AIN just before the opening of this year’s Paris show, Mitsubishi Aircraft senior executive vice president and executive chief engineer Kishi Nobuo reported that the four flight test vehicles operating out of Moses Lake, Washington, in the U.S. have completed 800 hours of flying, and that, despite the need for the design changes, the program has achieved all of its early objectives. Kishi added that original plans called for a total of some 2,500 hours of flying, and that the need to relocate components and reroute wiring in the airplane’s avionics bay will add few hours to the total.

Mitsubishi now expects to complete most flight testing by the end of 2018, ahead of certification the following year and first delivery to All Nippon Airways in 2020. The new schedule reflects no fewer than five major schedule delays, which together have set back expected certification by some seven years since program launch in 2008.

The need for the design changes that led to the latest two-year delay became apparent after a company engineering review last autumn, when Mitsubishi determined that the original design did not properly account for “extreme situations” such as water leakage or an explosion in the area of the avionics bay.

"Last summer to autumn, we reviewed all the MRJs configurations [at] the aircraft level,” said Kishi. “We decided to change...for example, electrical component location...Frankly speaking, we made a conclusion that it would take less time to do the design change than thinking more about how to prove the safety [of] the previous design to obtain type certification.

“However, these design changes will not affect aircraft performance, fuel consumption, or functionality of systems,” he added. “We will be able to continue ongoing flight testing with the current test aircraft configuration and be able to obtain certification flight test data of performance, flight characteristics, etcetera for the type certificate. The design change will not affect aircraft structure either.”

Other changes revealed by flight testing include what Kishi described as minor modifications to the airplane’s environmental control system. Mitsubishi Aircraft engineering strategy manager Lindsey McDaniel characterized that discovery as more of a typical flight test finding, however. The finding arose out of extreme temperature testing of MRJ FTA-4 at Eglin Air Force Base in Florida this spring. “So far there’s nothing that’s been particularly surprising relative to standard flight test OEM programs,” she said. “We’ve actually made quite a bit of progress completing the Eglin testing. It’s significant; there’s a lot of logistical preparation that’s involved and all of the system teams have to do proper evaluation to confirm we’re ready to do those types of tests...So we’ve had a standard amount of findings. As we mentioned, from Eglin we found items in the chamber that we’re going to improve. So we continue to add good data from our flight test program, but I wouldn’t say there’s been anything particularly surprising.”   

Apart from a fifth prototype now in Japan conducting ground testing, Mitsubishi will add another flight test vehicle to the program to help validate the design changes and speed certification, said Kishi. He added that the company might deploy a second additional flight test airplane depending on the final results of the design change and the scope of the rework for the airplanes already built. Mitsubishi has now has started assembly of five production airplanes, one of which it will use as the first extra flight test example.

Processing of flight-test data takes place at Mitsubishi’s engineering center in Seattle, established in August 2015 in collaboration with locally based AeroTec specifically to administer MRJ testing in the U.S. Along with some 400 Mitsubishi Aircraft engineers, about 200 AeroTec employees work on the MRJ program in Seattle and at the Moses Lake flight test center.

While All Nippon Airways continues as the program’s launch customer, it remains unclear when the two customers that account for most of the MRJ’s backlog—SkyWest Airlines and Trans States Airlines of the U.S.—would take their first MRJ90s. In fact, the MRJ90 still does not fit within the weight limitations stipulated by pilot union scope clauses among the big three U.S. network carriers, leaving SkyWest and Trans States unable to commit to firm delivery dates. Both customers carry options to switch their choice from the MRJ90 to the MRJ70, certification of which Mitsubishi expects to occur roughly a year after its larger sibling. Kishi said Mitsubishi has begun assembling the first MRJ70 test article but noted that the timing of first flight depends largely on MRJ90 progress. “Mainly we have to concentrate on the MRJ90,” he explained. “The timing will be decided after considering MRJ90 development.”

Meanwhile, rival manufacturer Embraer of Brazil has moved back its schedule for entry into service of the new E175-E2 by about a year, from 2020 to 2021, for the same reason Mitsubishi finds itself in an uncertain position over MRJ deliveries to U.S. customers.

Most recently, Delta Air Lines pilots on December 1 ratified an agreement that maintains the 86,000 pound mtow and 76-seat capacity limits on airplanes operated by their regional affiliates until 2020, meaning those airlines could not operate neither the MRJ90 nor E175-E2. A contract extension that maintains similar restrictions reached with United Airlines pilots in January runs until 2019, while American Airlines’ contract becomes amendable in 2020.